I played a level 20 Dervish/Tempest optimized for AC last game, and got 33 just standing around. If she moved first (almost always did) she started applying feats and class features and got to 46 easy, and higher if she traded away BaB with Improved Combat Expertise.
I found in that game that AC is really not enough at high levels. Good saves are very important, and playing tactically VERY important.